Filter bypass monitoring system

ABSTRACT

A method and apparatus for sealing the opposed side edges of a fluid treating belt filter ( 3 ) by employing an inflatable elastic tube ( 18 ). Opposed sealing surfaces are spaced apart from each other defining a gap there between which can be brought into sealing relationship by activation of the tube ( 18 ). The tube ( 18 ) being tested prior to and during sealing. Fluid that bypasses the seal are collected for rycycle.

BACKGROUND OF THE INVENTION

[0001] This invention relates to filter systems and more particularly toa fluid filter bypass monitoring system which, during both filtering andfilter regenerating operations, assists in proper sealing between dirtyand clean fluid sides of the system and, at the same time, assists inrecovering residual fluid filtering materials.

[0002] It is known in the filtration art to use various types ofarrangements to seal the lateral edges of longitudinally advancablefilter media. Examples include relying on the weight of drive chains tourge the filter media against support members as disclosed in Hirs, U.S.Pat. No. 3,087,620 and Anderson, U.S. Pat. No. 5,008,007; usingresilient sealing strips as disclosed in Hindi, U.S. Pat. No. 3,358,834;special vacuum box sealing members as disclosed in Ishigaki, U.S. Pat.No. 3,677,411; dam members on the undersides of the filter media whichinteract with underlying shelf members as disclosed in Lee, U.S. Pat.No. 4,220,539, and even inflatable seal tubes as disclosed in Bratten,U.S. Pat. No. 5,601,729. Each of the aforementioned seal techniques hasdisadvantages. Particularly the use of inflatable seal tubes is subjectto failure if the tubes leak or burst.

[0003] It is also known to provide inflatable seals to seal spacebetween adjacent parallel surfaces and to test the effectiveness of theseal by measuring pressure in chambers formed between the seal and thesealed interfaces. Examples of such seals are disclosed in Godfrey, U.S.Pat. No. 4,214,760 and Brooking, U.S. Pat. No. 4,908,179. In both ofthese patents, the testing mechanism accomplishes testing when thesurfaces to be sealed are in sealed position, the testing beingaccomplished by a comparatively complex series of alternatively spacedtest probes passing through an enlarged upper end of a flexible sealabove the inflatable portion of such flexible seal, the distal ends ofthe probes extending through each flexible seal into a chamber which isformed between the flexible seal and the members to be sealed so as tomeasure pressure in such formed chamber. Not only is such an arrangementcomparatively complex and costly in construction, operation andmaintenance, but in addition, the testing measurement function is ofquestionable value since it punctures a portion of the flexible sealmaterial and testing is accomplished upon actual sealing rather thanprior to such sealing.

[0004] Despite the efforts of the prior art, there has remained a needfor reliable measures to prevent dirty liquid from circumventing thelateral edges of a longitudinally movable, elongated filter medium andentering a clean filtrate chamber.

SUMMARY OF THE INVENTION

[0005] In the present invention, an economical and straightforwardstructural sealing, arrangement is provided which is comparatively moreefficient in construction, maintenance and operation, the inventivesealing arrangement requiring a minimum of parts in the novel apparatusand a minimum of steps in the novel method. Further, the presentinvention, recognizing the possibilities of fluid leakage during sealingoperations and the possibilities of the presence of residual fluidsduring seal open regenerating operations, provides a unique andstraightforward fluid and particulate capture arrangement so as toaccommodate for such possible contingencies. The novel capturearrangement, like the above discussed sealing arrangement, also requiresa minimum of parts in the apparatus and a minimum of steps in themethod.

[0006] In accordance with a first aspect of the invention, an filteringapparatus is provided having opposed lateral walls and comprising areceiving tank for dirty liquid to be filtered; an adjacent filtratechamber for filtered liquid; and a longitudinally movable filter mediuminterposed between the receiving tank and the filtrate chamber such thatliquid can flow from the receiving tank through the filter medium,whereby the liquid is filtered, and into the filtrate chamber; thefilter medium having opposed lateral edges extending longitudinallyalong the lateral walls of the filter apparatus; selectively actuatableseal members extending along the lateral edges of the filter medium forsealing the lateral edges against leakage during filtering operations;the seal members being deactuatable to release the filter medium toenable the filter medium when loaded with filtered solids to be movedlongitudinally to interpose a fresh section of the filter medium betweenthe receiving tank and the filtrate chamber; and a leakage collectordisposed under the lateral edges of the filter medium for capturing anydirty liquid which leaks through the seal members when actuated or whichis released when the seal members are deactuated to permit longitudinalmovement of the filter medium.

[0007] In further aspect of the invention, a filtering apparatus isprovided having opposed lateral walls and comprising a receiving tankfor dirty liquid to be filtered; an adjacent filtrate chamber forfiltered liquid; and a longitudinally movable filter medium interposedbetween the receiving tank and the filtrate chamber such that liquid canflow from the receiving tank through the filter medium, whereby theliquid is filtered, and into the filtrate chamber; the filter mediumhaving opposed lateral edges extending longitudinally along the lateralwalls of the filter apparatus; selectively actuatable seal membersextending along the lateral edges of the filter medium for sealing thelateral edges against leakage during filtering operations; the sealmembers comprising opposed members on opposite sides of the lateraledges of the filter medium, and at least one of the members beingmovable toward or away from the other member, and the seal members beingdeactuatable to release the filter medium to enable the filter mediumwhen loaded with filtered solids to be moved longitudinally to interposea fresh section of the filter medium between the receiving tank and thefiltrate chamber; and a restoring spring for urging the at least onemovable member away from the other member.

[0008] In yet another aspect of the invention, a filtering apparatus isprovided having opposed lateral walls and comprising a receiving tankfor dirty liquid to be filtered; an adjacent filtrate chamber forfiltered liquid; and a longitudinally movable filter medium interposedbetween the receiving tank and the filtrate chamber such that liquid canflow from the receiving tank through the filter medium, whereby theliquid is filtered, and into the filtrate chamber; the filter mediumhaving opposed lateral edges extending longitudinally along the lateralwalls of the filter apparatus; selectively actuatable seal membersextending along the lateral edges of the filter medium for sealing thelateral edges against leakage during filtering operations; the sealmembers being deactuatable to release the filter medium to enable thefilter medium when loaded with filtered solids to be movedlongitudinally to interpose a fresh section of the filter medium betweenthe receiving tank and the filtrate chamber; an actuator comprising aninflatable and deflatable tube for actuating the seal members, and apressure sensor or pressure indicator for monitoring the pressure in theinflatable and deflatable tube.

[0009] It is also an aspect of the invention to provide a method offiltering particulate matter from a particulate laden liquid streamcomprising passing the particulate laden liquid stream through afiltering zone including a particulate laden liquid inlet and a cleanliquid outlet with a movable, elongated filter medium having opposedside edges interposed between the inlet and the outlet; selectivelyactuating sealing members positioned along the opposed side edges of theelongated the filter medium to a closed sealing position during filteroperation and deactuating the seal member to an open position when thefilter medium becomes loaded with filtered particles and it is necessaryto renew the filtering capability of the apparatus, thereby releasingthe filter medium for longitudinal movement; longitudinally moving thefilter medium to position a fresh section thereof between the dirtyliquid receiving tank and the clean filtrate chamber; thereafteractuating the sealing members to reclose the sealing members andre-commencing filtering operations, and monitoring the performance ofthe sealing members.

[0010] Various other features of the present invention will becomeapparent to one skilled in the art upon reading the disclosure set forthherein.

[0011] More particularly, the present invention provides a fluid filterapparatus comprising fluid receiving tank means having opposed sidewalls, the tank means including a first tank section to receive a dirtyfluid to be filtered and a successive second tank section to receiveclean fluid after it has been filtered; longitudinally extending porousfilter means having opposed longitudinally extending side edges, thefilter means being intermittently moveable between filtering andregenerating operations in a plane between the first and second tanksections, the filter means being adapted to separate out particulatematter during a filtering operation from the dirty fluid passing fromthe first tank section to the second tank section; sealing means to sealthe opposite side edges of the filter means between the first and secondtank sections during the filtering operations, the sealing meansincluding pairs of first and second opposed sealing members positionedon opposite faces of the side edges of the filter means, at least one ofthe sealing members of each pair being moveable relative the othersealing member; an actuating member to activate relative movement ofeach of the opposed sealing member pairs to sealed position duringfiltering operations and to a bypass open position during intermittentmovement of the filter means for regenerating operations; a bypassmonitoring system including verification means to verify operability ofthe actuating member prior to positive movement of the actuating memberto sealing position for filtering operations; and residual fluid andparticulate capture means to capture residual fluid and particulatematter due to possible leakage during sealed filtering operations andduring open regenerating operations.

[0012] In addition, the present invention provides a method of filteringparticulate matter from a particulate laden fluid stream comprisingpassing a particulate laden fluid stream through a filtering zoneincluding a particulate laden fluid stream inlet and a clean fluidstream outlet with opposed side edges of a filtering member extendingbetween the particulate laden fluid inlet and the clean fluid outlet;selectively activating sealing members to closed sealing position andregeneratively open position along the opposed side edges of a filteringmember during fluid treating and regenerative steps, respectively;verifying the activating sealing step during the open regenerative stepwhen fluid treating operations cease; and capturing residual fluid andparticulates from the sealing and regenerative steps.

[0013] It is to be understood that various changes can be made by oneskilled in the art in one or more of the several parts and in one ormore of the several steps of the inventive apparatus and method,respectively, disclosed herein without departing from the scope orspirit of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention will be described in further detail hereinafterwith reference to illustrative preferred embodiments shown in theaccompanying drawings in which:

[0015]FIG. 1 is an isometric partially broken away view of a pressurefilter to schematically illustrate applicable portions of the presentinvention;

[0016]FIG. 2 is a schematic side view of the pressure filter of FIG. 1,disclosing separately driven permanent and disposable filter belts;

[0017]FIG. 3 is an enlarged cross-sectional partial view of oneembodiment of the present invention, taken along line 3-3 of FIG. 1;

[0018]FIG. 4 is an enlarged cross-sectional view similar to that of FIG.3, disclosing a modified embodiment of the present invention, and

[0019]FIG. 5 is a schematic representation of the seal monitoringarrangement for the filter arranngement of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0020] Referring to the drawings, FIGS. 1 and 2 disclose a partiallybroken way automatic belt type pressure filter 2 which incorporates thefeatures of the invention. It is to be understood that the inventivefeatures disclosed herein are not to be considered as limited to thedisclosed pressure filter of FIGS. 1 and 2 but that the features can beemployed with other sealing arrangements where fluid passage and sealingare involved.

[0021] As can be seen in the pressure filter apparatus 2 disclosed inFIGS. 1 and 2, the filter housing includes independently andsynchronously driven longitudinally extending, endless, permanent,filter belt 3 and disposable filter belt 5 mounted above a fixedlongitudinally extending fluid pervious foraminous structural supportplate 4. The filter belts 3 and 5 are synchronously moved along fluidpervious fixed plate 4, with disposable filter material 5 being unwoundfrom a supply source 6 and conveyed to a disposal container at end 7 ofapparatus 2. Although both permanent and disposable belts 3 and 5 aredisclosed, it is to be understood that fluid filter may alternativelycomprise only a disposable filter medium 5, or only a permanent filtermedium 3. Either or both filter medium types (i.e., disposable belt 5and/or permanent belt 3) is intermittently moveable when loaded withfiltered particles so as to be capable of moving clean fluid treatingfilter media into the fluid stream to be treated whenever needed inorder to maintain the filtering capacity of the apparatus.

[0022]FIG. 3 of the drawings shows only one filter media belt lateraledge sealing arrangement 8, but it is to be understood that a similarmirror image sealing arrangement 8 can be employed along the oppositelateral edge of a filter belt.

[0023] The sealing arrangement 8 disclosed includes a pair of alignedlongitudinally extending and facing sealing members 9 and 11 defining alongitudinally extending gap 12 therebetween along which thelongitudinal side edge of filter belt travels. The upper sealing member9, as shown, is static, and the lower sealing member 11 is moveable soas to sealingly close gap 12 and thereby seal the lateral edge of thefilter medium 3, 5 therebetween. It is to be understood that it wouldalso be possible, if desired, to reverse the static-moveable sealingarrangement and have the fixed member 9 on the bottom and movable member11 on the top, or even to have both cooperating sealing members moveabletoward and away from each other.

[0024] In the embodiment of FIG. 3, lower sealing member 11 is ofchannel form, having a U-shaped cross-section, and as an outer channelmember, surmounts another, smaller, fixed, inner channel member 13, alsohaving a U-shaped cross-section, with the opposed side legs of channelmember 13 including spaced, opposed aligned slots 14 through which theopposite extremities of a pin 16 extend to be secured to the oppositeside legs of moveable lower surmounting outer sealing member 11. Thus,outer sealing member 11 is not only moveable relative upper fixedsealing member 9 but it also is moveable relative the surmounted smallerfixed inner channel member 13. Due to the relative sizing of thecooperating lower, super-mounted, moveable and fixed channel members 11and 13, a longitudinally extending chamber 17 is formed between upperbase surface of channel member 13 and the lower or inner base surface ofchannel member 11. This chamber 17 serves to accommodate elongated,hollow, elastic tube 18 therein, so that the hollow tube 18 is betweenlower moveable channel member 11 and lower fixed channel member 13. Thedefined chamber for hollow elastic tube 18 is connected to fluidpneumatic or hydraulic source represented by air line 19 through asuitable valve arrangement so that tube 18 can be inflated to movechannel member 11 toward fixed member 9 and/or deflated to allow channelmember 11 to retract away from fixed member 9.

[0025] Disposed within the lower inner fixed channel member 13 insurrounding relation to pin 16 is a helical coil spring 21 with theextremities thereof abutting the inner face of the base leg of the outermoveable lower channel member 11. Accordingly, when hollow tubing 18 isinflated, advantageously by air (pneumatically) through air line 19,moveable, lower, outer channel member 11 is moved against the force ofspring 21 into sealing relation against the fixed upper member 9, withthe lateral edges of filter belts 3 and 5 extending into longitudinallyextending gap 12 between the opposed sealing members 9 and 11, therebysealing gap 12 and the lateral edges of filter belts 3 and 5 betweenfixed sealing member 9 and moveable channel member 11. When the filtermedia 3 and 5 become loaded with filtered solids so that the rate offiltration decreases to an unacceptable level, as indicated by anincrease in the pressure drop across the filter media, hollow elastictubes 18 are deflated by releasing the fluid pressure in the tubes 18 byswitching valves 22, schematically shown in FIG. 5. Spring 21 acts tomove the moveable sealing channel member 11 away from fixed member 9,thereby opening gap 12, deflating tube 18, and releasing filter belts 3and 5. Once belts 3 and 5 are released from betwen the seal members 9and 11, the filter media can be advanced to position a fresh section ofthe filter medium between the receiving tank and the filtrate chamber.The seals are then re-closed, and filtration can begin anew.

[0026] Referring to the schematic diagram of FIG. 5 of the drawings,when gap 12 is in open position, the four hollow elastic tubes 18 whichare disclosed are deflated. It is to be noted that in the embodimentdisclosed in FIG. 5, four inflatable tubes 18 in oppositely spacedaligned pairs of two are employed along the opposed side edges of filterbelts 3 and 5; however, it is to be understood that other tubingarrangements can be used. In the schematic arrangement of FIG. 5, areversible ball and solenoid valve 22, 23 is shown for each hollowelastic tube 18. Each valve 22 is responsive to the operation of asolenoid 23. The system of FIG. 5 is responsive to the intermittentmovement of filter belts 3 and 5 with gap 12 opened accordingly to allowtesting air to be introduced through line 24 into a hollow tube 18 so asto determine measurable pressure in tube 18 through pressure sensors orindicators 26. With this arrangement, it is thus possible to determineby pressure indicators 26 whether there is any leakage in seal actuatinghollow tubes 18 and whether sealing throughout can be appropriatelyrelied upon. Also, if a sealing tube fails when the seal members 9, 11are closed during a filtering operation, the pressure sensor orindicator 26 will show it and can be immediately used to actuate analarm and/or shut down the filter apparatus before dirty liquid canpenetrate to the filtrate chamber.

[0027] Referring again to FIGS. 2 and 3 of the drawings, it can be seenthat as another feature of the invention, gravity flow, inclined tankmembers 27 can be positioned below opposed longitudinally extendingfilter edges to capture any residual liquid and particulate matter thatmight enter gap 12 during gap opening for appropriate recycle anddisposal.

[0028] Alternatively, plate members 28 can be installed as shown in FIG.4 along lower seal members 11, 13. Plate members 28 form a collectingchamber between the lower seal member and the sidewall of the filterapparatus. These chambers catch and retain any dirty liquid which eitherleaks through the seal when the seal is closed or which passes throughthe seal when the seal is opened and prevent such dirty liquid fromentering the clean filtrate chamber. Particulate laden dirty liquidcaptured by these collecting chambers can be purged with compressed airor flushed out with a liquid stream and recycled or disposed of, asappropriate.

[0029] In accordance with still another aspect of the present invention,a method of filtering particulate matter from a particulate laden liquidstream is provided comprising the steps of passing the particulate ladenliquid stream through a filtering zone including a particulate ladenliquid inlet and a clean liquid outlet with an movable, elongated filtermedium having opposed side edges interposed between the inlet and theoutlet; selectively actuating sealing members positioned along theopposed side edges of the elongated the filter medium to a closedsealing position during filter operation and deactuating the seal memberto an open position when the filter medium becomes loaded with filteredparticles and it is necessary to renew the filtering capability of theapparatus, thereby releasing the filter medium for longitudinalmovement; longitudinally moving the filter medium to positioning a freshsection thereof between the dirty liquid receiving tank and the cleanfiltrate chamber; thereafter actuating the sealing members to reclosethe sealing members and re-commencing filtering operations, andmonitoring the performance of the sealing members.

[0030] In preferred embodiments of the filtering method, the sealingmembers are actuated by inflating a tubular actuator, and theperformance of the sealing members is monitored by monitoring thepressure in the tubular actuator with a pressure sensor, gauge orindicator. Failure of the tubular actuator during operation will beindicated by a rapid decrease in pressure. It is also possible byshutting off the air supply to the tubular actuator and then monitoringthe pressure in the tube, to detect even pinhole leaks which coulddevelop into a later catastrophic failure of the tube. In this way,tubular actuators which are in danger of failing can be identified andreplaced during regular maintenance intervals of the filteringapparatus, thereby avoiding catastrophic failures which could require anemergency shut-down of the filtering apparatus and consequentinterruption of plant operations.

[0031] Another preferred embodiment of the method of the inventioninvolves capturing any dirty liquid which may leak through the seal whenclosed or which may pass through the seal when it is opened to permitadvancement of the filter media to regenerate the filtering capacity ofthe apparatus. As noted above, this may be achieved by use of acollecting trough 27 positioned underneath the seal members, or by meansof a seal plate 28 which prevents dirty liquid from flowing past theseal members into the clean filtrate chamber. Captured or collectedresidual dirty liquid may then be recycled to filtration or disposed of,as appropriate.

[0032] The foregoing description and examples have been set forth merelyto illustrate the invention and are not intended to be limiting. Sincemodifications of the described embodiments incorporating the spirit andsubstance of the invention may occur to persons skilled in the art, theinvention should be construed broadly to include all variations fallingwithin the scope of the appended claims and equivalents thereof.

What is claimed is:
 1. A liquid filter apparatus having opposed lateralwalls and comprising a receiving tank for dirty liquid to be filtered;an adjacent filtrate chamber for filtered liquid; and a longitudinallymovable filter medium interposed between said receiving tank and saidfiltrate chamber such that liquid can flow from said receiving tankthrough the filter medium, whereby the liquid is filtered, and into thefiltrate chamber; said filter medium having opposed lateral edgesextending longitudinally along the lateral walls of the filterapparatus; selectively actuatable seal members extending along thelateral edges of said filter medium for sealing said lateral edgesagainst leakage during filtering operations; said seal members beingdeactuatable to release said filter medium to enable the filter mediumwhen loaded with filtered solids to be moved longitudinally to interposea fresh section of the filter medium between said receiving tank andsaid filtrate chamber; and a leakage collector disposed under thelateral edges of the filter medium for capturing any dirty liquid whichleaks through the seal members when actuated or which is released whenthe seal members are deactuated to permit longitudinal movement of thefilter medium.
 2. A liquid filter according to claim 1, wherein saidseal members comprise opposed members on opposite sides of the lateraledges of said filter medium, at least one of said members being movabletoward or away from the other member.
 3. A liquid filter according toclaim 2, further comprising a restoring spring for urging said at leastone movable member away from the other member.
 4. A liquid filteraccording to claim 1, wherein said leakage collector comprises acollecting trough extending along a lateral wall of said apparatusunderneath the seal members.
 5. A liquid filter according to claim 4,wherein said collecting trough is an inclined, gravity flow trough.
 6. Aliquid filter according to claim 1, wherein said leakage collectorcomprises a plate extending between a lower seal member and a lateralwall of said apparatus, said plate forming a collecting chamber betweensaid lateral wall and said lower seal member which catches and retainsany dirty liquid which leaks through said seal members when actuated orwhich circumvents a lateral edge of said filter medium underneath alower seal member when the seal members are deacutated.
 7. A liquidfilter according to claim 1, wherein said longitudinally movable filtermedium comprises an endless belt of permanent filter material.
 8. Aliquid filter according to claim 1, wherein said longitudinally movablefilter medium comprises an elongated strip of disposable filter materialfed from a supply roll at one end of the apparatus and collected in adisposal chamber at the other end of the apparatus.
 9. A liquid filteraccording to claim 1, wherein said longitudinally movable filter mediumcomprises an endless belt of permanent filter material and a superposedstrip of disposable filter material fed from a supply roll at one end ofthe apparatus and collected at in a disposal chamber at the other end ofthe apparatus.
 10. A liquid filter according to claim 1, wherein saidfilter material is supported on an underlying foraminous plate.
 11. Aliquid filter according to claim 1, wherein said seal members areactuated by an actuating device comprising an inflatable tube.
 12. Aliquid filter according to claim 11, wherein said tube is selectivelyinflatable to actuate the sealing members and deflatable to deactuatethe sealing members.
 13. A liquid filter according to claim 12, whereinsaid tube is inflated and deflated by means of a reversible ball andsolenoid valve.
 14. A liquid filter according to claim 12, furthercomprising a pressure sensor or pressure indicator for monitoring thepressure in said tube.
 15. A liquid filter according to claim 12,further comprising a deflating mechanism for automatically deflatingsaid tube when pressure in said tube is released.
 16. A liquid filteraccording to claim 15, wherein said deflating mechanism comprises amovable seal member disposed adjacent said tube and a restoring springwhich urges said movable seal member against said tube.
 17. A liquidfilter according to claim 2, wherein the movable seal member comprises afixed, first u-shaped channel member having elongated slots in legsthereof, a second, movable channel member arranged partially surroundingsaid first channel member such that legs of said second channel memberare positioned outside and laterally adjacent the legs of the firstchannel member and an actuator compartment is formed between the firstand second channel members, at least one pin member extending from thelegs of the second channel member through the slots in the first channelmember, and an actuator in said actuator compartment which when actuatedurges second channel member toward the other seal member.
 18. A liquidfilter according to claim 17, wherein said actuator comprised aselectively inflatable and deflatable tube.
 19. A liquid filteraccording to claim 18, further comprising a restoring spring which urgesthe first and second channel members together, said spring forciblydeflating said tube when a valve on an inflation line is opened torelease pressure from the tube.
 20. A liquid filter apparatus havingopposed lateral walls and comprising a receiving tank for dirty liquidto be filtered; an adjacent filtrate chamber for filtered liquid; and alongitudinally movable filter medium interposed between said receivingtank and said filtrate chamber such that liquid can flow from saidreceiving tank through the filter medium, whereby the liquid isfiltered, and into the filtrate chamber; said filter medium havingopposed lateral edges extending longitudinally along the lateral wallsof the filter apparatus; selectively actuatable seal members extendingalong the lateral edges of said filter medium for sealing said lateraledges against leakage during filtering operations; said seal memberscomprising opposed members on opposite sides of the lateral edges ofsaid filter medium, and at least one of said members being movabletoward or away from the other member, and said seal members beingdeactuatable to release said filter medium to enable the filter mediumwhen loaded with filtered solids to be moved longitudinally to interposea fresh section of the filter medium between said receiving tank andsaid filtrate chamber, the movable member including a fixed U-shapedchannel member having legs, and a movable U-shaped channel memberarranged partially surrounding said fixed channel member such that legsof said movable channel member are positioned outside and laterallyadjacent the legs of the fixed channel member so that the fixed channelmember provides lateral support to the movable channel member; and arestoring spring for urging the at least one movable member away fromthe other member.
 21. A liquid filter apparatus having opposed lateralwalls and comprising a receiving tank for dirty liquid to be filtered;an adjacent filtrate chamber for filtered liquid; and a longitudinallymovable filter medium interposed between said receiving tank and saidfiltrate chamber such that liquid can flow from said receiving tankthrough the filter medium, whereby the liquid is filtered, and into thefiltrate chamber; said filter medium having opposed lateral edgesextending longitudinally along the lateral walls of the filterapparatus; selectively actuatable seal members extending along thelateral edges of said filter medium for sealing said lateral edgesagainst leakage during filtering operations; said seal members beingdeactuatable to release said filter medium to enable the filter mediumwhen loaded with filtered solids to be moved longitudinally to interposea fresh section of the filter medium between said receiving tank andsaid filtrate chamber; an actuator comprising an inflatable anddeflatable tube for actuating said seal members, and a pressure sensoror pressure indicator for monitoring the pressure in said inflatable anddeflatable tube.
 22. A liquid filter according to claim 21, furthercomprising a deflating mechanism for automatically deflating said tubewhen pressure in said tube is released.
 23. A liquid filter according toclaim 22, wherein said deflating mechanism comprises a movable sealmember disposed adjacent said tube and a restoring spring which urgessaid movable seal member against said tube.
 24. A method of filteringparticulate matter from a particulate laden liquid stream comprisingpassing the particulate laden liquid stream through a filtering zoneincluding a particulate laden liquid inlet and a clean liquid outletwith a movable, elongated filter medium having opposed side edgesinterposed between the inlet and the outlet; selectively actuatingsealing members positioned along the opposed side edges of the elongatedthe filter medium to a closed sealing position during filter operationand deactuating the seal member to an open position when the filtermedium becomes loaded with filtered particles and it is necessary torenew the filtering capability of the apparatus, thereby releasing thefilter medium for longitudinal movement; longitudinally moving thefilter medium to position a fresh section thereof between the dirtyliquid receiving tank and the clean filtrate chamber; thereafteractuating the sealing members to reclose the sealing members andre-commencing filtering operations, and monitoring the performance ofthe sealing members.
 25. A method according to claim 24, wherein thesealing members are actuated by inflating a tubular actuator with airfrom an air supply, and the performance of the sealing members ismonitored by monitoring the pressure in the tubular actuator with apressure sensor, gauge or indicator.
 26. A method according to claim 25,further comprising shutting off the air supply to the tubular actuatorand then monitoring the pressure in the tube to detect leaks in thetube.
 27. A method according to claim 24, further comprising capturingany dirty liquid which may leak through the seal when closed or whichmay pass through the seal when it is opened to permit advancement of thefilter media to regenerate the filtering capacity of the apparatus.